Macrophage-secreted factors promote a profibrotic phenotype in human preadipocytes.
White adipose tissue (WAT) in obese humans is characterized by macrophage accumulation the effects of which on WAT biology are not fully understood. We previously demonstrated that macrophage-secreted factors impair preadipocyte differentiation and induce inflammation, and we described the excessive fibrotic deposition in WAT from obese individuals. Microarray analysis revealed significant overexpression of extracellular matrix (ECM) genes in inflammatory preadipocytes. We show here an organized deposition of fibronectin, collagen I, and tenascin-C and clustering of the ECM receptor alpha5 integrin, characterizing inflammatory preadipocytes. Anti-alpha5 integrin-neutralizing antibody decreased proliferation of these cells, underlining the importance of the fibronectin/integrin partnership. Fibronectin-cultured preadipocytes exhibited increased proliferation and expression of both nuclear factor-kappaB and cyclin D1. Small interfering RNA deletion of nuclear factor-kappaB and cyclin D1 showed that these factors link preadipocyte proliferation with inflammation and ECM remodeling. Macrophage-secreted molecules increased preadipocyte migration through an increase in active/phosphorylated focal adhesion kinase. Gene expression and neutralizing antibody experiments suggest that inhibin beta A, a TGF-beta family member, is a major fibrotic factor. Interactions between preadipocytes and macrophages were favored in a three-dimensional collagen I matrix mimicking the fibrotic context of WAT. Cell-rich regions were immunostained for preadipocytes, proliferation, and macrophages in the vicinity of fibrotic WAT from obese individuals. In conclusion, an inflammatory environment leads to profound modifications of the human preadipocyte phenotype, producing fibrotic components with increased migration and proliferation. This phenomenon might play a role in facilitating the constitution of quiescent preadipocyte pools and eventually in the maintenance and aggravation of increased fat mass in obesity.
Keophiphath
Mayoura
M
Institut National de la Santé et de la Recherche Médicale (INSERM) Unité 872, Centre de recherche des Cordeliers, 15 rue de l'école de Médecine, 75005 Paris, France.
Achard
Vincent
V
Henegar
Corneliu
C
Rouault
Christine
C
Clément
Karine
K
Lacasa
Danièle
D
D052438:Adipocytes, White / Q000166:cytology* / Q000502:physiology*; D001483:Base Sequence; D002448:Cell Adhesion; D002450:Cell Communication; D002454:Cell Differentiation; D002465:Cell Movement; D049109:Cell Proliferation; D002478:Cells, Cultured; D017077:Culture Media, Conditioned; D016326:Extracellular Matrix Proteins / Q000235:genetics; D005355:Fibrosis; D015870:Gene Expression; D019940:Genes, bcl-1; D006801:Humans; D007249:Inflammation / Q000235:genetics / Q000473:pathology / Q000503:physiopathology; D008264:Macrophages / Q000378:metabolism*; D008954:Models, Biological; D009765:Obesity / Q000473:pathology / Q000503:physiopathology; D010641:Phenotype; D034741:RNA, Small Interfering / Q000235:genetics; D051996:Transcription Factor RelA / Q000037:antagonists & inhibitors / Q000235:genetics
D017077:Culture Media, Conditioned; D016326:Extracellular Matrix Proteins; C498143:RELA protein, human; D034741:RNA, Small Interfering; D051996:Transcription Factor RelA